Browsing by Author "Chen, Pin-Yi"

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Correlation of Microstructures and Conductivities of Ferroelectric Ceramics Using Complex Impedance Spectroscopy
(2010-06-01)
Chen, Pin-Yi
;
Chou, Chen-Chia
;
Tseng, Tseung-Yuen
;
Chen, Haydn
;
電子工程學系及電子研究所
The microstructures and conductivities of lead-free ceramics [Bi(0.5)(Na(1-x)K(x))(0.5)]TiO(3) with x = 0.18 (BNKT) and lead-based ceramics of x(0.94PbZn(1/3)Nb(2/3)O(3) + 0.06BaTiO(3)) + (1 - x)PbZr(y)Ti(1-y)O(3) with x = 0.5, y = 0.52 (PBZNZT) were investigated. Experimental results show that the activation energy of grain boundary conductivity is higher than that of grain conductivity for the BNKT system, indicating that the Bi(2)O(3) evaporation of grains induces an easy conduction path through grains. However, the activation energy of grain boundary conductivity is lower than that of grain conductivity for the PBZNZT system, which might be attributed to the charged particles in the amorphous phase at grain boundaries, participating in the conduction process. A conduction model of both grain and grain boundary conductivities was proposed, and the microstructural characteristics and AC impedance data of ferroelectric ceramics correlate fairly well, suggesting that impedance spectroscopy is an efficient characterization technique for the grain boundary engineering of ferroelectric ceramics. (C) 2010 The Japan Society of Applied Physics DOI: 10.1143/JJAP.49.061505
Second Phase and Defect Formation in Bi(0.5)Na(0.5-x)K(x)TiO(3) Ceramics
(2010-06-01)
Chen, Pin-Yi
;
Chou, Chen-Chia
;
Tseng, Tseung-Yuen
;
Chen, Haydn
;
電子工程學系及電子研究所
The second phase and defect formation mechanisms of [Bi(0.5)(Na(1-x)K(x))(0.5)]TiO(3) (BNKT100x) ceramics were investigated using electron microscopy, X-ray photoelectron spectroscopy (XPS), and electrical properties measurement. Experimental results indicated that second phase formation induces Bi-rich regions and compositional inhomogeneity within the matrix owing to the thermodynamic stability of potassium titanate. The Ti valence transition for BNKT ceramics sintered in air might be ascribed to the formation of secondary phase and low oxygen atmosphere, rather than simply attributed to the volatilization of bismuth. Li substitution at the A-site in BNKT ceramics suppresses formation of the second phase and Ti valence transition. Appropriate atmosphere control during material processing, such as sintering at higher oxygen pressure, and post oxidization annealing suppress oxygen vacancies and titanium valence transition, and therefore decrease the leakage current as well as improve electrical properties. (C) 2010 The Japan Society of Applied Physics DOI: 10.1143/JJAP.49.061506
Second Phase and Defect Formation in Bi0.5Na0.5-xKxTiO3 Ceramics
(2010-06-01)
Chen, Pin-Yi
;
Chou, Chen-Chia
;
Tseng, Tseung-Yuen
;
Chen, Haydn
;
電子工程學系及電子研究所
The second phase and defect formation mechanisms of [Bi-0.5(Na1-xKx)(0.5)]TiO3 (BNKT100x) ceramics were investigated using electron microscopy, X-ray photoelectron spectroscopy (XPS), and electrical properties measurement. Experimental results indicated that second phase formation induces Bi-rich regions and compositional inhomogeneity within the matrix owing to the thermodynamic stability of potassium titanate. The Ti valence transition for BNKT ceramics sintered in air might be ascribed to the formation of secondary phase and low oxygen atmosphere, rather than simply attributed to the volatilization of bismuth. Li substitution at the A-site in BNKT ceramics suppresses formation of the second phase and Ti valence transition. Appropriate atmosphere control during material processing, such as sintering at higher oxygen pressure, and post oxidization annealing suppress oxygen vacancies and titanium valence transition, and therefore decrease the leakage current as well as improve electrical properties. (C) 2010 The Japan Society of Applied Physics DOI: 10.1143/JJAP.49.061506